If you want statistics on neglect and abandonment, there are many. I can think of several cases off the top of my head where this sort of thing happened. A child's bones found in a garden and no record she was ever enrolled in a school or anything - her family moved away; there was a case of three children being found deceased in an attic I recently heard of where they never found the mother or the culprit, (who was likely also the mother), a case of a child sequestered in a small room, neglected and abused her entire life etc... countless cases of abandonment and discovery of unidentified bodies of babies and small children. Yes, unfortunately it is a "thing".